If you have the luxury of flying a route regularly you can see how generous or not the flight plan fuel is, regular short cuts and better cruising levels for instance. We have an interesting situation, where the plans for our NGs are spot on, but the classics tend to need a bit extra. Anyone else have this problem?
At the end of the day I believe strongly in the red face test. If you can explain at the end of the day why you did what you did and not go red in the face explaining to your superiors, then things are OK.
I see the self evident target as landing at my destination as close to minimum diversion fuel as often as makes sense. I think landing with less is at least as bad as landing with more. In many cases landing with more reflects that you have saved fuel rather than wasted it!